1. Field of the Invention
The present invention relates to an endosseous dental implant having a dimpled surface texture for use in prosthetic reconstruction of the mandible, maxilla, or any craniofacial bones.
2. Description of the Prior Art
The use of cylindrical endosseous dental implants for treatment of various dental, medical, or other conditions is generally well known in the oral and maxillofacial surgery and dental prosthetics field. It has been estimated that in the United States alone, there are in excess of 30 million people that are edentulous in one or both jaws which could benefit from the implantation of 100 million cylindrical endosseous dental prosthetics. Cylindrical endosseous dental implants are commonly used in full arch or partial arch prosthetic reconstruction, secondary reconstruction of craniofacial caner resection, or replacement of single teeth.
The efficacy of a dental implant is primarily dependent upon the surrounding bone's adaptive reformation around and bonding to the implant surface. In particular, the geometry and the quality of such bone reformation determines how much load the bone can resist.
First generation dental implants were typically anchored by mechanical attachment of press-fitted titanium prosthetic implants in the mandible or maxilla. A significant problem of such mechanical fixing resulted from inadequate bone reformation and bonding and consequent failure of the bone when subject to functional loading and resultant shear stresses.
Another cause of dental implants' failure derives from imprecise drilling of the bony site in preparation of the implant. Frequently, the holes are formed by a succession of drillings with several drillbits in incrementally larger diameters selected to correspond with the shape of the implant post. Implant geometry combined with the increased source of operator error introduced by the successive drillings may not result in the desired socket. For example, an oversized socket in which the implant fits loosely may be formed, and is not immediately immobilized resulting in movement when subjected to the stresses of mastication leading to the delayed healing and possible failure of the implant.
Over the past decade, procedures for enhancement of anchoring of dental implants by biochemical bonding of craniofacial bone to an implant surface coated with a substrate have been developed to address the problems of mechanical fixation in the absence of biochemical interfacing. In particular, hydroxylapatite (HA) coatings have been developed which provide for exceptionally strong bonding with bone, in comparison to other biocompatible metal substrates. Typically, HA is plasma sprayed on titanium surfaces.
The biochemical enhancement of bonding occurring at HA-bone interfaces have been observed through histologic and mechanical tests. Histologic tests demonstrate that a HA coating on a titanium alloy provides an osteophilic substrate for enhanced bony proliferation. Such studies indicate that there exists an affinity between bone mineralization and HA, which contrast to the dyschrony between bony proliferation and titanium. The enhanced bonding provided by HA coatings increases the mechanical fixation/anchoring strength of a dental implant two or three times, as compared to metal dental implants of the same geometry.
However, there remain significant problems with HA-coated implants, which largely relate to mechanical limitations of the coating thickness. The mechanical performance of the HA-coated implant is generally inversely related to coating thickness, i.e., a thinner coating of HA has increased mechanical performance. The approximate lower limit for coating thickness is between 10 and 15 microns, the amount of HA surface which may dissolve during the bone implant bonding process. A thickness of about 50 microns is optimal. The upper limit for coating thickness is between 100 and 150 microns, above which susceptibility to shortened service life from fracture or other modes of failure due to shear and tensile fatigue. In view of those limitations on HA coating thickness, the biomedical industry customarily applies coatings ranging between approximately 30 and 90 microns thick.
Unfortunately, notwithstanding the enhanced bonding provided by HA coatings on dental implants, the rate of failure due to shear and tensile fatigue is high as even low loads cannot be withstood along the wall of dental implants with conventional surfaces. Thus, even low functional loads may cause cracking and dislodging of the bone-HA-implant and interfaces.
An additional drawback of HA coatings as applied to prior art surfaces, including threaded or straight-walled implants is cracking, scratching, and stripping of HA often occurs when an implant contacts adjacent surfaces as it is inserted in a jawbone.
Thus, the need for a dental prosthesis with sufficiently strong bonding to the adjacent bony formations of the maxilla and mandible to withstand stress loads, particularly resultant shear and tensile stresses along the shear interface, applied to the dental arches persists.